[Jewelry making - Article 00011] - Re: [Orchid] Shellac removal

[Ian W. Wright]

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>     There is a device called an "Immersion heater" which is a small
>     electric heating coil - originally invented by my high school
>     biology teacher in the 1940's. There is some common lab procedure
>     in elementary biology lab which requires heating alcohol.

    Good idea Marty. There's just one more safety thing I'd like to
    mention though for anyone who is planning to use the electric heater
    method. Because of the size of these heaters it is necessary to use
    much more alcohol than I would in my 1 inch copper end cap and, in
    addition, it is not so easy to control the violence of the boiling
    alcohol. So, as this will inevitably produce quite a lot of vapour
    and droplets, you must ensure that there are no open flames or
    burning cigarettes around as the vapour will flow along the bench
    and over the edge to the floor for quite a distance around  and
    could quite easily ignite and produce a broad area fire. Its true
    that a pure alcohol flame is virtually invisible but, when it is
    contaminated with shellac, (and I save the dirty alcohol for re-use
    in shellac removal as it will work for a long time in removing the
    bulk of the shellac and the piece can be given a final rinse in
    clean alcohol), the flame has a distinctly yellow tinge and can be
    readily seen. Even if you don't feel competent to extinguish any
    flames against the underside of the bench, the fact that you have
    the alcohol in a high-sided metal pan contains the fire and so,
    apart from the fact that the piece you are cleaning would be left
    with a dirty residue, you could safely set the pan on a fireproof
    soldering mat and let it burn itself out. Covering the pan with any
    kind of lid, damp cloth etc, will quickly extinguish the flames.
    Having a CO2 fire extinguisher around would be a good idea but you
    should use it carefully as I was present when a fireman was
    hospitalised trying to put out a simple fire with one. The fire was
    in the large fryer of a commercial kitchen and was relatively under
    control as the lid of the pan had been closed and was being covered
    with wet towels, however, the fireman decided to be proactive,
    lifted the lid and squirted the CO2 extinguisher into the pan. The
    gas hit the back and lid of the pan and caused a wave of burning
    boiling oil which shot out of the front of the pan and all down the
    front of the fireman. Fortunately his clothing protected him from
    the worst of it but he still had burnt hands and face and was in
    hospital for several days. 

Best Wishes
Ian
Ian W. Wright
Sheffield  UK

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